Why not eliminate the input buffer? (And a big thanks to March Audio!)

[Digital Mastering System]

I have a bench full of test instruments and all of them are single ended BNC. Oh, one spectrum analyzer has a balanced input (using a not so great transformer). I have a GHz Spectrum analyzer that's single ended. All scopes and the generators are SE. My HP noise meter is SE. I also have instrumentation transformers when I need them and a Tektronics Differential probe. To be honest I rarely use them because I usually don't need to use them.

It is true that the RCA connector itself is junk - as audopile (above) has said, BNC or others are superior connectors as is the XLR.

But the prevalence of balanced connections in high end gear is mostly fashion - it rarely actually fixes a problem that exists and is often worse noise wise than the the simpler SE configuration.

The usual 'HiFi' balanced connection is not really a pro +4dbm setup anyway. The pro stuff I worked on clipped at +28dbm (19Vrms if I'm not mistaken, 55v pk-pk; of course transformers make this possible with 15V rails).

 

[March Audio]

I have a bench full of test instruments and all of them are single ended BNC. Oh, one spectrum analyzer has a balanced input (using a not so great transformer). I have a GHz Spectrum analyzer that's single ended. All scopes and the generators are SE. My HP noise meter is SE. I also have instrumentation transformers when I need them and a Tektronics Differential probe. To be honest I rarely use them because I usually don't need to use them.
It is true that the RCA connector itself is junk - as audopile (above) has said, BNC or others are superior connectors as is the XLR.

But the prevalence of balanced connections in high end gear is mostly fashion - it rarely actually fixes a problem that exists and is often worse noise wise than the the simpler SE configuration.

The usual 'HiFi' balanced connection is not really a pro +4dbm setup anyway. The pro stuff I worked on clipped at +28dbm (19Vrms if I'm not mistaken, 55v pk-pk; of course transformers make this possible with 15V rails).

Im afraid all thats demonstrably not true when you enter the real world with actual different bits of kit connected together in a domestic or professional audio environment for the reasons explained.

Real world usage and application, even in the domestic environment, means that balanced will almost way's beat SE. If you don't believe me just take a look at Amirs DAC and amp tests to see which ones top the SINAD scores. All balanced.

There is nothing complex or expensive about a differential op amp input.

 

[Dion_Sinewave]

The Benchmark article begs the question why we’re not seeing more studio-grade equipment in audiophile circles. But maybe all the cryo treatments, directional fuses, etc. soak up the costs necessary to make this possible. It’s interesting that the equipment that does well in Amir’s reviews come predictably from brands with strong backgrounds in research (Harman/Revel) or studio work (RME, Genelec, Benchmark).

I could not agree more. It is strange isn’t it?

I’ve used pro gear in my system for a decade and aside from the aesthetics and initial learning curve I can’t understand why I don’t see that more often.

2 x Dolby Lake Contours configured in Stereo 4 way crossover and serious EQ.

 

[Xulonn]

Whilst this isn't always an overt problem it is interesting to see the number of threads on here talking about "computer noises".

My only sources are via HDMI and/or USB from a computer - an older Intel NUC5CPYB running Linux-based dedicated software. Although I never had hum and noise problems with my Teac AH01 (my first good quality DAC/Amp), I switched to XLR output to feed my amps when when I upgraded recently to using HDMI exclusively to my AVP (IOTAVX 7.1 4K). I figured it was an easy and inexpensive bit of preventive planning. No problems so far, and I think it is likely that I won't have problems in the future unless there is a mechanical connection problem.

 

[DonH56]

I have not read this whole thread but regarding levels and units:

Consumer level for years was -10 dBV, and professional gear +4 dBu. Different units... Just to add to the confusion 0 dBVU (0 on a VU meter) is also defined as +4 dBu. The "V" in dBV is for Volt so 0 dBV = 1 V; -10 dBV is about 316 mV. The "u" in dBu actually stands for unloaded and is derived from early telephony days where 600 ohms was a common impedance but folk wanted to know the source voltage when it was not connected to anything (unloaded). The unloaded voltage is just that; what you get when the driver (source) is unloaded (open-circuit voltage). The derivation of dBu comes from assuming 1 mW into 600 ohms, thus 0 dBu = 0.775 Vrms (power is voltage squared over resistance, or P = V^2/R, so V = sqrt(P * R) = sqrt(0.001 W * 600 ohms) = 0.7745966... V).

Why care about unloaded? In circuit network theory, open- and short-circuit analysis provides way to determine the characteristics of an unknown circuit ("black box"), but short-circuiting an unknown device is usually unwise Instead, you could measure it unloaded, then with a known load, and derive information about what's inside the box.

I have not seen audio gear rated in dBm except for telephone line gear. That is dB relative to 1 mW so of course you must define the impedance (R) you are using to calculate power. My world (RF/mW/mmW/Gb/s serial data links) uses mainly 50- and 100-ohm systems (though PCIe is 85 ohms, a strange value not worth getting into here but generally provides lower loss), and most single-ended RF systems are 50 ohms, so dBm is with respect to 1 mW into 50 ohms. A notable exception is the cable/satellite world which often uses 75-ohm systems. For the same signal voltage this saves power, typically at the expense of somewhat higher loss and lower bandwidth in a real-world system.

All the pro audio gear I have seen for many years uses dBu. Many pieces of gear have a "-10 dBV" switch to work with consumer or lower-level gear.

HTH - Don

 

[Panelhead]

I wonder where the love for single ended is coming from. Using Professional sources with balanced high output levels and lower overall gain amplifiers has worked out better for me.
When building my own chassis it gives the freedom to select from all the connectors available. Settled on NOS Amphenol 31-223 chassis jacks and 31-224 cable plugs. Better quality than any RCA’s, 1/4”, or XLR connector. Smaller, lower mass, wider bandwidth.

 

[mlee]

Whilst you are mostly correct (yes I have Dougs book and know the chapter ) single ended is not better. It has a fundamental flaw. That of ground loops. You will get noise currents flowing in the shield which will spoil any slight inherent noise advantage they have. Whilst this isnt always an overt problem it is interesting to see the number of threads on here talking about "computer noises".

Also a differential input using a modern op amp like the opa1612 is spectacularly quiet.

Yes, Douglas Self loads his question/answer a bit in that chapter by using that circuit but it was neat looking at the end result of the proposed lower noise solution.

 

[AnalogSteph]

When building my own chassis it gives the freedom to select from all the connectors available. Settled on NOS Amphenol 31-223 chassis jacks and 31-224 cable plugs. Better quality than any RCA’s, 1/4”, or XLR connector. Smaller, lower mass, wider bandwidth.

And over 20 bucks each if bought new. Last time I checked audio didn't really need connectors good to 2 GHz either - not unless you've got lots of RF floating around for one reason or another.

If I wanted small, I'd probably take a hard look at 5-pin Mini-XLR, two channels in one compact connector and not quite as exotic.

In any case, today I learned that what we are calling XLR actually is just XL, strictly speaking.

 

[DonH56]

Originally the Cannon X connector, added latching (L), then a synthetic rubber insulator (R), per Wikipedia.

Edit: Cannon, with two n's, thanks John!

 

[Matias]

I think that having needless gain is the core issue. And having gain steps, or better yet variable gain, is the ideal. This has guided my latest purchases: Mola Mola Makua is variable gain, RME ADI-2 DAC FS with AutoRef is gain steps + digital volume control.
My next amplifier I will surely pay attention to have the gain steps, or if not possible, at least set for maximum power at 4V RMS

 

[AudioJester]

So removing a gain stage improves performance.
All in one active speakers should be the best then? Like the really low distortion on the Kii3. Wonder if the hypex modules in that setup have an input buffer??

By the way Mr March, big fan of your products and have recommended them to people who have gone on to buy them. I remember in a local Aussie forum you slammed people for running hypex modules without an input buffer and a high output dac - in fact you called them "stupid", but now you years later you are doing it yourself???

 

[March Audio]

So removing a gain stage improves performance.
All in one active speakers should be the best then? Like the really low distortion on the Kii3. Wonder if the hypex modules in that setup have an input buffer??

By the way Mr March, big fan of your products and have recommended them to people who have gone on to buy them. I remember in a local Aussie forum you slammed people for running hypex modules without an input buffer and a high output dac - in fact you called them "stupid", but now you years later you are doing it yourself???

?

I would have criticised them for running from a passive volume control without a buffer but not from a high output dac.

I think you may have misread or missed the context of any comments.

 

[restorer-john]

Canon

Cannon with two 'n's. Not the printer people. I think they were made in Australia first, then the ITT/Cannon factory set up in Japan. It was a long time ago. Wasn't ITT a semiconductor/component fabricator in the 1960s/70s in Europe?

 

[TimF]

DMS -thank you for the devil's advocate position on the balanced v. single ended issue. Personally - roughly 55 years of dealing with RCA connectors has made me hate ,loath and despise them. But you make a pretty good case for it being the CONNECTORS that are the practical issue and NOT the cable configuration. I have circled around and sniffed the idea of converting my main system to BNC's or Camacs/Limo connectors for decades -a project-but much less of a epic than converting my mostly analog LP based stereo system to all balanced. I still think that from a purely mechanical point of view -XLR's pretty much smoke RCA's.

Re: Dion-Sionewave, What is the Sony piece of equipment specifically?

 

[restorer-john]

The usual 'HiFi' balanced connection is not really a pro +4dbm setup anyway. The pro stuff I worked on clipped at +28dbm (19Vrms if I'm not mistaken, 55v pk-pk; of course transformers make this possible with 15V rails).

They don't make preamplifiers like they used to.

Take the Pioneer Spec 1 from the late 1970s. It has +/-48V rails from the phono stage right through to the line output buffer. You can imagine what it can swing with a 600R source impedance...

Or the Kenwood LO-7CII. It has +/-47V rails, a ruler flat response to 500KHz and an output impedance well under 10R.

+/-15V rails are for babies.

 

[DonH56]

Cannon with two 'n's. Not the printer people. I think they were made in Australia first, then the ITT/Cannon factory set up in Japan. It was a long time ago. Wasn't ITT a semiconductor/component fabricator in the 1960s/70s in Europe?

Yes, yes, but ITT (International Telephone and Telegraph) is an old American company AFAIK... I'd forgotten about the ITT Cannon period.

Corrected.

Thanks John.

 

[Dion_Sinewave]

Re: Dion-Sionewave, What is the Sony piece of equipment specifically?

One of my MiniDisc players. I have 4.
For electronic music recorded directly from a phono stage they were unique as you could edit really effectively and I though they sounded exceptional. Obviously its far better now to record to a PC and edit with software but for a long time around 2000 I’d take one of these to a nightclub and record a DJ set live.

 

[MC_RME]

I have not seen audio gear rated in dBm except for telephone line gear. That is dB relative to 1 mW so of course you must define the impedance (R) you are using to calculate power.

There had been tons of pro audio gear referring to dBm (when I was young). Mostly broadcast stuff. They used transformers on input and output and followed the impedance matching technique, based on 600 Ohm. Luckily that's a thing of the past, dBm is an unused value for many years - at least in audio. But you still find 600 Ohm as reference in a lot of places.

 

[Burning Sounds]

It's still being used - although I suspect they may mean +4dBu

From the Mytek 8x192ADDA manual:

 

[DonH56]

There had been tons of pro audio gear referring to dBm (when I was young). Mostly broadcast stuff. They used transformers on input and output and followed the impedance matching technique, based on 600 Ohm. Luckily that's a thing of the past, dBm is an unused value for many years - at least in audio. But you still find 600 Ohm as reference in a lot of places.

Yes, agreed, I should have included broadcast gear, but was thinking of consumer and stage/studio gear.

It's still being used - although I suspect they may mean +4dBu

From the Mytek 8x192ADDA manual:

View attachment 82101

Curious to see an analog audio output spec'd at 4 dBm and 75 ohms; seems a curious juxtaposition. I might expect to see that for AES. I wonder if that is +4 dBm terminated in 75 ohms? Very low load for an analog audio input. But I have not kept up with pro gear lately.